Escapement mechanism



May 15, 1962 A. MOCCAND ETAL 3,034,630

ESCAPEMENT MECHANISM Filed March 13, 1961 5 13 M 7 1/ 9 g a n I II a 12 //V)// /T0Q5 United States Patent 3,034,630 ESCAPEMENT MECHANISM Adrien Moccand and Gustave Gagnebin, Yverdon,

Switzerland, assignors to Paillard S.A., Vaud, Switzer-.

land, a corporation of Switzerland Filed Mar. 13, 1961, Ser. No. 95,347 Claims priority, application Switzerland Mar. 29, 1960 Claims. (Cl. 197-88) The invention relates to an escapement mechanism, particularly for the carriage of a typewriter, comprising a toothed movable member, a retaining pawl and an escapement pawl carried by a brace and co-operating with the teeth of this movable member, the advance of a step being obtained by the disengagement of the escapement pawl and the simultaneous engagement of the retaining pawl, the escapement pawl being then displaced for engaging 'at another point of the teeth, the retaining pawl being then disengaged and the escapement pawl moved by one tooth of the movable member until its movement is stopped by a stop.

In the case of a typewriter, the carriage is accelerated under the action of the barrel spring each time that the escapement mechanism is actuated. The carriage attains a relatively high speed and during its stopping by the escapement pawl, the carriage rebounds. These rebound-s are very annoying, as they may disturb the alignment of the next typing stroke. When this rebound is very considerable, it is even possible to obtain two superposed ty'pings.

The present invention has for its object to remedy this inconvenience. It has for its object an escapement mechanism of the said type, characterized in that the retaining pawl is carried by a part pivotally mounted on the brace, the stop of the escapement pawl being mounted on this part, a shock-absorbing device being provided for braking the movement to which this part is subjected relatively to the brace under the action of the movable member.

One form of construction of the subject of the invention is shown diagrammatically in the accompanying drawings, wherein:

FIG. 1 is a view in elevation showing the escapement and retaining pawls and the escapement wheel.

FIG. 2 is a view in plan of the part located below the escapement wheel.

The escapement mechanism illustrated comprises a block-support 1 provided with two adjustable pivots 2 and 3 on which is hinged a brace 4 provided with an operating lever 5. This lever is actuated by the typing mechanism of a typewriter each time that the carriage is to be advanced one step.

The brace 4 carries an escapement pawl 6 and a bridle 7 provided with a tooth 8 constituting a retaining pawl. The pawl 6 is hinged about two spindles, of known type, and not shown in detail, and subjected to the action of two springs 9 and 10. This pawl is maintained in the position indicated in FIG. 2 by the spring 9 against the action of which it can be displaced, by means, not shown, particularly for releasing the carriage during the tabulation. The extremity of the pawl 6 is adapted to engage between the teeth of an escapement wheel 11 disposed above the brace 4 and subjected to a torque by reason of the return drum of the carriage. This torque tends to cause the escapement wheel 11 to turn in an anticlockwise direction, with reference to FIG. 1.

Under the action of the wheel 11, the pawl 6 is maintained pressed against an adjustable stop 12, secured to the bridle 7. The spring 10 tends to withdraw the pawl 6 away from this stop 12 by causing it to pivot about an axis passing through two pivots of which the ends 13 and 14 are visible in FIG. 2.

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The bridle 7 is hinged to the brace 4 by means of two pivots 15 and 16, of which the axis is parallel to that passing through the pivots 13 and 14. This bridle carries an assembly of spring blades 17 which is secured by means of a nut 18 screwed on the threaded end of the part 12 forming a stop for the pawl 6. Plates of synthetic resin, such as nylon, are interposed between the elastic blades forming the spring 17, the last of these plates being placed between the surface of the brace 4 and the spring constituted by the blades 17.

The operation of this escapement mechanism is as follows:

In the normal position, a tooth of the escapement wheel 11 is retained by the escapement pawl 6, which bears against the stop 12. During the typing on the machine, means, not shown, act on the lever 5 and cause the brace 4 to pivot about pivots 2 and 3. It thus results that the escapement pawl 6 is disengaged from the tooth by which it was retained, whilst the retaining pawl simultaneously comes into engagement with this tooth so as to prevent the escapement wheel 11 from turning. When the escapement pawl is disengaged from the wheel 11, it pivots under the action of the spring 10 and about the pivots 13 and 14 in such a manner that its end moves towards the left of FIG. 1, through a distance a little less than that separating two consecutive teeth of the wheel 11. When the brace 4 effects a rocking movement in the reverse direction, the retaining pawl allows the tooth of the wheel 11, which was retained, to escape so that this latter commences to turn in an anti-clockwise direction. The following tooth of the wheel 11 comes to bear against the retaining pawl 6 and, under the action of the return spring of the carriage, causes this to pivot until it meets the stop 12. The force exerted by the retaining pawl 6 on the stop 12 causes the bridle 7 to pivot about its pivots 15 and 16, at the same time as the blade spring 17 exerts a friction against the surface of the brace 4, against which it bears obliquely. The movement of the bridle 7 is limited by a part 19 thereof abutting against a portion 20 of the brace 4.

The friction exerted between the spring 17 and the brace 4 absorbs a large portion of the kinetic energy of the carriage and provokes a substantial diminution of the speed until the moment at which the parts 19 and 20 of the stop come into contact one with the other.

The bridle 7 pivots in an opposite direction under the action of the spring 17 during the functioning of the escapement mechanism, that is to say when the retaining pawl 8 is disengaged from an escapement tooth and until the pawl 6 abuts against the part 12. In this manner, at the moment of coming into contact of the pawl with the stop 12, the bridle 7 can efiect the necessary pivoting for obtaining deadening. Preferably, the blades 17 constituting the spring, may be pre-tensioned in such a manner as to exert a substantial friction against the brace 4 from the start of the movement which it effects when leaving the position shown in FIG. 1. This deadening of the shock at the end of the movement of the carriage limits practically any rebound and permits of increasing the force of the return spring of the carriage. Tests have shown that an increase of 40% of the speed of typing is possible on machines equipped with such an escapement mechanism. Further, this mechanism, which is very simple and not expensive, renders escapement more silent.

It will be understood that numerous modifications may be applied to the escapement mechanism described and that it may be advantageous to provide a deadening de vice on escapement mechanism intended for other use than that for the control of the carriage of a typewriter. In a general manner it is advantageous that the deadening is effected by means of an elastic element adapted a l to be deformed by exerting friction against one of the two parts with which it co-ope rates for deadening the shock.

We claim:

1. An escapement mechanism, particularly for the carriage of a typewriter, comprising a toothed movable member, a brace, a retaining pawl and an escapement pawl carried by said brace and co-operating with the teeth of said movable member, a stop for said escapement pawl, the advance of a step being obtained by the disengagement of said escapement pawl and the simultaneous engagement of said retaining pawl, said escapement pawl being then displaced for engagement at another point of said teeth, said retaining pawl being then disengaged and said escapement pawl moved by one tooth of said movable member until its movement is stopped by said stop, a part carrying said retaining pawl, said part being pivotally mounted on said brace, the stop of said escapement pawl being mounted on said pivotally mounted part, and a shock-absorbing device for braking the movement to which said part is subjected relatively to said brace under the action of said escapement pawl when stopping said movable members.

2. A mechanism according to claim 1, wherein said shock-absorbing device includes an elastic element, said elastic element being placed between said part and said brace in such a manner that the pivoting of said part deforms said element while causing said element to exert friction between said part and said brace.

3. A mechanism according to claim 2, wherein said elastic element is constituted by at least one spring blade, one end of said blade being disposed in such a manner as to meet obliquely a bearing surface of said brace during the movement of said stop.

4. A mechanism according to claim 3, wherein a plate of synthetic resin is interposed between said bearing surface and said spring blade.

5. A mechanism according to claim 1, wherein said pivotal part carries a pile of spring blades constituting said shock-absorbing device, said pile bearing against the surface of said brace, a blade of syntheticresin being interposed between each spring blade, and means limiting the movement which said pivotal part may elfect under the action of said escapement pawl moved by said mov- 20 able member.

References Cited in the file of this patent 

